Roller grill

ABSTRACT

A roller grill includes a housing structure adapted to support the roller grill; a plurality of tubular heating surfaces mounted between a first end of the housing structure and a second end of the housing structure; a first side housing coupled to the first end of the housing structure; a second side housing coupled to the second end of the housing structure, at least one of the first side housing or the second housing including a pressurized plenum maintainable at a plenum air pressure that is greater than a tubular air pressure of an inner volume of the plurality of tubular heating surfaces; and a drive assembly at least partially enclosed in the first side housing or the second side housing, the drive assembly configured to rotatably drive the plurality of tubular heating surfaces.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. Ser. No. 14/177,997 filed Feb.11, 2014 and titled “Roller Grill”

TECHNICAL BACKGROUND

This disclosure relates to a roller grill or griddle for heating and/orreheating pre-cooked food product.

BACKGROUND

Various apparatus are used to heat and/or reheat prepared consumerpre-cooked food products. In some instances, cylindrically shapedpre-cooked food products, such as hotdogs, tacquitos, cheese burgerbites, and sausage links, may be prepared using a roller grillapparatus, which may include a number of heated, rotating tubes uponwhich the pre-cooked food products rest and rotate. While the heatconducting and/or radiating from the tubes and the rotation of the tubesallow the pre-cooked food products to be heated substantially uniformly,these features can also impose detrimental effects on other componentsof the roller grill apparatus. For example, heat conducted and/orradiated from the ends of the tubes is transferred to rotating drivemechanism components in contact with the ends of the tubes, such aschains, lubricants, bearings, and other components. The heat conductedand/or radiated through these components, as well as the mechanicalengagement of these components with one another during operation of theroller grill apparatus, can cause gradual deterioration and eventualfailure of such components.

Conventionally, roller grills and/or griddles used for heating and/orreheating pre-cooked food products have used chain drive assemblies todrive (e.g., rotate) tubular heating surfaces on which the pre-cookedfood products may be placed. The chain drive assemblies typicallyutilize a metallic chain that engages metallic sprockets mounted on thetubular heating surfaces. Due in part to the metal-on-metal contact, aswell as the heat energy conducted through and/or radiated from thesprockets and chain from the tubular heating surfaces (and othercomponents of conventional roller grills), the chain drive assembly mayrequire regular maintenance (e.g., lubrication, adjustment of the chainand/or the sprockets to maintain suitable engagement, and otherwise).Without such regular maintenance, conventional roller grills oftenexperience high failure rates.

In some instances, pre-cooked food products must be heated to a minimuminternal temperature in order to, for example, kill bacteria that cancause food related illness. For instance, certain standards (e.g., NSFInternational) have been established that require pre-cooked foodproduct to be heated to a minimum internal temperature for safetyreasons.

SUMMARY

In a general embodiment, a roller grill includes a housing structureadapted to support the roller grill; a plurality of tubular heatingsurfaces mounted between a first end of the housing structure and asecond end of the housing structure; a first side housing coupled to thefirst end of the housing structure; a second side housing coupled to thesecond end of the housing structure, at least one of the first sidehousing or the second housing including a pressurized plenummaintainable at a plenum air pressure that is greater than a tubular airpressure of an inner volume of the plurality of tubular heatingsurfaces; and a drive assembly at least partially enclosed in the firstside housing or the second side housing, the drive assembly configuredto rotatably drive the plurality of tubular heating surfaces.

A first aspect combinable with the general embodiment further includes afan coupled to the housing structure and in airflow communication withthe pressurized plenum and an ambient environment that surrounds theroller grill.

In a second aspect combinable with any of the previous aspects, the fanis configured to circulate a flow of ambient air into the pressurizedplenum to maintain the plenum air pressure greater than the tubular airpressure.

A third aspect combinable with any of the previous aspects furtherincludes a cover plate mountable to the one of the first side housing orthe second housing that includes the pressurized plenum to at leastpartially seal against an airflow between the pressurized plenum and theambient environment independent of the flow of ambient air.

In a fourth aspect combinable with any of the previous aspects, thecover plate includes at least one relief opening that includes anairflow pathway between the pressurized plenum and the ambientenvironment.

In a fifth aspect combinable with any of the previous aspects, theairflow pathway between the pressurized plenum and the ambientenvironment includes an adjustable opening area based on at least one ofthe plenum air pressure or the tubular air pressure.

In a sixth aspect combinable with any of the previous aspects, the otherof the first side housing or the second housing includes a secondpressurized plenum that is maintainable at a second plenum air pressurethat is greater than the tubular air pressure of the inner volume of theplurality of tubular heating surfaces.

A seventh aspect combinable with any of the previous aspects furtherincludes a second fan coupled to the housing structure and in airflowcommunication with the second pressurized plenum and the ambientenvironment that surrounds the roller grill.

In an eighth aspect combinable with any of the previous aspects, thesecond fan is configured to circulate a second flow of ambient air intothe second pressurized plenum to maintain the second plenum air pressuregreater than the tubular air pressure.

In a ninth aspect combinable with any of the previous aspects, a surfacetemperature measured along a length of a first tubular heating surfaceof the plurality of tubular heating surfaces is within a range ofbetween ±2° F. and ±5° F.

In a tenth aspect combinable with any of the previous aspects, the driveassembly includes a beltless direct drive assembly that includes atleast one drive gear in direct contact with a transfer gear, which inturn is in direct or indirect contact with at least one idler gear,which in turn is in direct contact with at least one tube gear.

In an eleventh aspect combinable with any of the previous aspects, atleast one of the drive gear, the transfer gear, the idler gear, or thetube gear includes a non-metallic gear.

In a twelfth aspect combinable with any of the previous aspects, thedrive assembly includes at least one drive gear driveably coupled to abelt or chain, which in turn is driveably coupled to at least one tubegear.

In a thirteenth aspect combinable with any of the previous aspects, thedrive assembly includes a slip clutch motor.

In another general embodiment, a method includes providing a rollergrill that includes a housing structure adapted to support the rollergrill, a plurality of tubular heating surfaces mounted between a firstend of the housing structure and a second end of the housing structure,and to a drive assembly, a first side housing coupled to the first endof the housing structure, and a second side housing coupled to thesecond end of the housing structure; rotatably driving the plurality oftubular heating surfaces with the drive assembly; pressurizing a plenumenclosed within one of the first or second side housings; andmaintaining, based on the pressurization, a plenum air pressure greaterthan a tubular air pressure of an inner volume of the plurality oftubular heating surfaces.

In a first aspect combinable with the general embodiment, pressurizing aplenum enclosed within one of the first or second side housings includescirculating an airflow into the plenum with a fan coupled to the housingstructure and in airflow communication with the plenum and an ambientenvironment that surrounds the roller grill.

A second aspect combinable with any of the previous aspects furtherincludes mounting a cover plate mountable to the one of the first orsecond side housings that encloses the plenum; and at least partiallysealing against an airflow between the plenum and the ambientenvironment independent of the airflow into the plenum.

A third aspect combinable with any of the previous aspects furtherincludes providing at least one relief opening in the cover plate; andflowing a portion of the airflow from the plenum through the reliefopening.

A fourth aspect combinable with any of the previous aspects furtherincludes adjusting an opening area of the relief opening based on atleast one of the plenum air pressure or the tubular air pressure.

A fifth aspect combinable with any of the previous aspects furtherincludes circulating a second airflow into a second plenum enclosedwithin the other of the first or second side housings; and maintaining,based on the second airflow circulation, a second plenum air pressuregreater than the tubular air pressure of the inner volume of theplurality of tubular heating surfaces.

In a sixth aspect combinable with any of the previous aspects,circulating a second airflow into a second plenum enclosed within theother of the first or second side housings includes circulating thesecond airflow into the second plenum with a second fan coupled to thehousing structure and in airflow communication with the second plenumand the ambient environment that surrounds the roller grill.

In a seventh aspect combinable with any of the previous aspects, asurface temperature measured along a length of a first tubular heatingsurface of the plurality of tubular heating surfaces is within a rangeof between ±2° F. and ±5° F.

In an eighth aspect combinable with any of the previous aspects,rotatably driving the plurality of tubular heating surfaces with thedrive assembly includes driving a drive gear with a motor; driving atleast one transfer gear with the drive gear; driving at least one idlergear with the transfer gear; and driving at least one tube gear with theidler gear.

In a ninth aspect combinable with any of the previous aspects, at leastone of the drive gear, the transfer gear, the idler gear, or the tubegear includes a non-metallic gear, and the drive assembly includes abeltless and chainless drive assembly.

In a tenth aspect combinable with any of the previous aspects, rotatablydriving the plurality of tubular heating surfaces with the driveassembly includes driving a drive gear with a motor; moving a belt orchain with the drive gear; driving at least one tube gear with themoving belt or chain.

In an eleventh aspect combinable with any of the previous aspects,rotatably driving the plurality of tubular heating surfaces with thedrive assembly includes driving the plurality of tubular heatingsurfaces with a slip clutch motor.

Various embodiments of a roller grill according to the presentdisclosure may include one or more of the following features. Forexample, the roller grill that includes one or more pressurized plenumsmay help prevent (e.g., all or partially) heat from escaping from anumber of tubular heating surfaces into an ambient environment through aheat transfer pathway that does not include the heating surfaces,themselves. In another example, one or more non-metallic gears (ormetallic gears) may be cooled in a pressurized plenum of the rollergrill. In some examples, a pressurized plenum of the roller grill mayfacilitate a more even heat distribution across one or more tubularheating surfaces. In some examples, the pressurized plenum may preventor help prevent heat from escaping through ends of the tubular heatingsurfaces. Thus, in some examples, the roller grill may be more energyefficient and more economical to operate compared to conventional rollergrills. As yet a further example, the roller grill may heat food productmore evenly across an entire area of heating surfaces (e.g., tubularrollers). This may, in some examples, reduce product from over cooking,under cooking, burning, or deformation, thereby providing a food productthat is free of bacteria, edible, and maintains a pleasing appearance toa consumer. As yet a further example, the roller grill that includes apressurized plenum may maintain contactable non-heating surfaces (e.g.,a housing) at a temperature that is safe for human contact withoutburn-related injuries.

These general and specific embodiments may be implemented using adevice, system or method, or any combinations of devices, systems, ormethods. The details of one or more embodiments are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIGS. 1A-1E illustrate views of an example embodiment of a roller grillthat includes a direct drive system and one or more pressurized plenums;

FIGS. 2A-2C illustrate views of an example embodiment of a roller grillthat includes a belt drive system and one or more pressurized plenums;

FIGS. 3A-3B illustrate views of another example embodiment of a rollergrill that includes a belt drive system and one or more pressurizedplenums;

FIG. 4 illustrates a side view of an example embodiment of a rollergrill that includes a belt drive system and one or more pressurizedplenums;

FIGS. 5A-5B illustrate views of example embodiments of a roller grilltube in accordance with the present disclosure;

FIGS. 6A-6D illustrate an example worm gear that may be used in a rollergrill according to the present disclosure; and

FIGS. 7A-7D illustrate side views of a portion of an example embodimentof a roller grill that includes one or more pressurization assemblies.

DETAILED DESCRIPTION

This disclosure relates to apparatus for heating and/or reheatingprepared consumer pre-cooked food products, and more particularly, toroller grills and/or griddles used for heating and/or reheatingcylindrically shaped pre-cooked food products, such as hotdogs andsausage links. Although in some embodiments, a roller grill according tothe present disclosure may only heat and/or reheat a pre-cooked foodproduct, in other embodiments, a roller grill according to the presentdisclosure may cook a raw food product.

In a general embodiment, a roller grill includes two side housings, abottom housing, and multiple heating tubes that are disposed parallel toone another, across a volume defined between upper regions of oppositepanels of the two side housings, and above the bottom housing. Theheating tubes are positioned sufficiently close to one another, suchthat their positioning allows a pre-cooked food product tosimultaneously rest atop two adjacent heating tubes. The heating tubesare further designed to rotate 360 degrees and have outer surfaces thatare adapted to transfer heat to pre-cooked food products, therebyallowing the heating tubes to heat and/or reheat pre-cooked foodproducts that rest atop the heating tubes.

Each of the side housings of the roller grill may include or form apressurized plenum that, in some aspects, are maintained at an airpressure greater (e.g., slightly or significantly) than an air pressureof the heating tubes (e.g., an air pressure of an interior volume of thetubular heating surfaces). In some aspects, the air pressure in apressurized plenum of the roller grill may be equal to the air pressureinside the heating tubes to prevent or help prevent the heat (e.g.,generated by an electric resistance heater positioned in the interiorvolume of the tubes) from escaping into the plenum rather than the tubesurface and into food product. In some aspects, the pressurized plenummay be substantially sealed against unwanted air leakage out of theplenum (e.g., into an ambient environment) while also allowing someairflow out of the plenum.

In some aspects, the air pressure in the pressurized plenums may bebalanced with the air pressure in the interior volumes of the heatingtubes so that minimal or insignificant airflow into or out of theheating tubes (e.g., into the plenums) occurs. For example, inconventional roller grills that do not include pressurized plenums inthe side housings, significant airflow from the interior volumes ofheating tubes may convectively transfer heat (e.g., generated byelectric resistance heat installed in the interior volumes) into theside housings. Such heat transfer may degrade a performance and/orcomponents of a drive assembly that rotates the heating tubes. Such heattransfer may also waste energy and money. Further, such heat transfermay result in uneven temperatures along the heating surfaces of theheating tubes. For instance, in some conventional roller grills,temperature variation along a length of a heating tube may be as much asabout 50° F. (from 225° F. to 175° F.) (or about 29° C., from 108° C. to79° C.) along a length of a particular tube (e.g., from end to end).Further, in conventional roller grills, heat may be undesirablytransferred to other components of the roller grill, such as the sidehousings, which may reach up to 240° F. (116° C.).

In some embodiments of a roller grill with one or more pressurizedplenums, an air moving device (e.g., a fan) may be positioned tocirculate an airflow into the plenums to maintain the air pressure. Insome aspects, there may be a 1:1 ratio of air moving devices andpressurized plenums; in some aspects, there may be a greater than 1:1ratio. Such airflow may help maintain or maintain the plenum at apositive pressure relative to the air pressure in the interior volumesof the heating tubes. Further, in some aspects, in order to maintain orhelp maintain this positive pressure without overpressurizing theplenum, one or more relief outlets may be formed in the side housings,thereby providing for an outlet for plenum air to escape into an ambientenvironment. Overpressurization of the plenums may result in severalissues. For example, if the air pressure in the pressurized plenums ismuch greater than the air pressure of the interior volumes of theheating tubes, a cooling airflow may be driven (e.g., by the pressuredifferential) into the interior volumes, thereby undesirably cooling theheating tubes. Also, overpressurization may result in deformation ofside housing panels.

A roller grill that includes one or more pressurized plenums may alsoinclude a variety of drive systems that drive (e.g., rotate) the tubularheating surfaces. In each instance, the pressurized plenum(s) may helpcool the drive assembly, cool other components of the roller grill(e.g., housing), and maintain a more consistent temperature of theroller tubes. For example, in some aspects, the roller grill may includea belt drive assembly having worm gears that provide rotary motion tothe heating tubes. For example, the belt drive assembly can be driven bya motor that provides rotary motion to a timing belt that transfers themotion to a timing pulley, which further rotates a shaft on which wormgears are mounted and engage spur gears that are coupled to ends of theheating tubes. In some embodiments, the belt drive assembly can havetiming pulleys coupled to the ends of the heating tubes and multipleidler pulleys that provide alternating heating and cooling cycles,respectively, for the timing belt during operation of the roller grill.In some examples, the timing pulleys can be maintained on the ends ofthe heating tubes by TEFLON™ flanges.

As another example, the roller grill may include a chain drive assemblyhaving sprockets that provides rotary motion to the heating tubes. Forexample, the chain drive assembly can be driven by a motor that providesrotary motion to a chain, which transfers the motion to sprocketscoupled to the ends of the heating tubes.

In other examples, the roller grill may have a direct drive assemblythat includes a drive gear coupled to a motor and in engagement with oneor more transfer gears configured to transfer rotational motion of thedrive gear to matched sets of gears directly coupled to heating tubes.The gears may, in some embodiments, be spur gears. In some embodiments,the gears may be helical spur gears. In some embodiments, the gears maybe non-metallic, such as, for example, a high-temperature plastic, Insome embodiments, for example, one or more gears directly coupled toheating tubes may be a high-temperature plastic such as, for example,polystyrene, nylon, TEFLON™, polyethylene, polypropylene, polyvinylchloride and polytetrafluoroethylene (PTFE), and other plastic material)that has a continual duty max temperature rating of between about 250°F. (121° C.) and about 500° F. (260° C.). In some embodiments, forexample, one or more transfer and/or idler gears may be ahigh-temperature plastic that has a continual duty max temperaturerating of between about 120° F. (49° C.) and about 200° F. (93° C.).

FIGS. 1A-1E illustrate views of an example embodiment of a roller grill100 that includes a direct drive system and one or more pressurizedplenums. The roller grill 100 can be used for heating and/or reheatingpre-cooked food products, such as, for example, cylindrically shapedpre-cooked food products including hotdogs, sausage links, and otherproducts. With reference to FIG. 1A in particular, the roller grill 100includes two side housings 105 a and 105 b and a bottom housing 110 thatis attached to and disposed between lower regions of panels of the twoside housings 105 a and 105 b. The weight of the roller grill 100 issupported by multiple legs 115 that are mounted underneath and nearcorners of the bottom housing 110. The roller grill 100 further includesmultiple heating tubes 120 that are disposed parallel to one another,across a volume defined between upper regions of opposite panels of thetwo side housings 105 a and 105 b, and above the bottom housing 110. Theheating tubes 120 are positioned sufficiently close to one another, suchthat their positioning allows a pre-cooked food product 125 tosimultaneously rest atop two adjacent heating tubes 120. One or moreannular shaped dividers 130 may be mounted on one or more heating tubes120 in order to prevent contact between two pre-cooked food products 125resting atop common heating tubes 120 or to restrict lateral movement ofpre-cooked food products 125 resting atop the heating tubes 120.

In some embodiments, the roller grill 100 may be approximately 36 inches(91.44 cm) in total length, and the heating tubes 120 may beapproximately 35.625 inches (90.49 cm) in length. In some examples, thewall thickness of a heating tube may be between approximately 5/64inches (0.20 cm) and approximately ⅛ inches (0.32 cm). In some examples,the width of the roller grill 100 may depend on the number of heatingtubes 120 included within the roller grill 100. In some examples, theroller grill 100 can include multiple (e.g., 4, 8, 16, or other number)heating tubes 120.

In some embodiments, the heating tubes 120 have outer surfaces that areadapted to transfer heat to pre-cooked food products 125 (e.g.,non-stick surfaces, cleanable surfaces, or otherwise). The heating tubes120, in some embodiments, are further designed to rotate 360 degrees,which consequently rotates the pre-cooked food products 125 360 degreesthat are in contact with the heating tubes 120. The heating tubes 120may be heated by multiple electric resistive heat elements. In someembodiments, at least one of the electric resistive heat elements may bedisposed within a bore of at least one of the heating tubes 120. In someexamples, the heat conducted to the surfaces of the heating tubes 120allows them to heat/and or reheat the pre-cooked food products 125. Insome instances, the electric resistive heat elements can enable thesurface temperatures of the heating tubes 120 to reach up to 300° F.(149° C.). In any event, the heating tubes 120 can heat the pre-cookedfood products 125 to an internal temperature of about 160° F. (71° C.),or other temperature, to ensure that any bacteria is killed and/oreliminated.

As illustrated, the roller grill 100 may also include a drip plate 180extending between the side housings 105 a and 105 b and underneath theheating tubes 120. In some embodiments, the drip plate 180 may define abottom side of a volume extending from directly underneath the heatingtubes 120 to the drip plate 180 and between the side housings 105 a and105 b. Such a volume, in some embodiments, may define a sanitary volumeinto which no mechanical components of the roller grill 100 (e.g.,gears, motors, shafts, and other components) may extend. The drip plate180 may, in some embodiments, be a cleanable surface that catchesdrippings and other solids and/or liquids from the pre-cooked foodproduct 125.

In some embodiments, the roller grill 100 can include a controller 104that sets the roller grill 100 to operate in one or more heating modes.For example, the heating modes may include a “Preparation” mode thatheats pre-cooked food products 125 to a set minimum preparationtemperature (e.g., 160° F. (71° C.) internal) or a “Ready-to-Serve” modethat maintains the internal temperature of the pre-cooked food products125 at a set serving temperature by cycling the heat on and off. In someexamples, the preparation temperature of the heating tubes 120 may reachup to 300° F. (149° C.). In some examples, the serving temperature ofthe heating tubes 120 may reach up to 240° F. (116° C.) in order tomaintain an internal pre-cooked food product temperature in the range of140-160° F. (60-71° C.). The roller grill 100 can further be designed tooperate in other heating modes (e.g., a timed heating mode, an overnightheating mode, a “wake up” heating mode, and others).

In some aspects, the controller 104 can increase or decrease an amountof heating power supplied by the heating elements 151 based on one ormore measured criteria. For example, in some aspects, electrical power(e.g., voltage or current) supplied to the heaters 151 can be variedbased on a sensed temperature of the tubes 120 (e.g., temperature ofouter heating surfaces). In another example, electrical power (e.g.,voltage or current) supplied to the heaters 151 can be varied based on atemperature differential between a sensed temperature of the tubes 120(e.g., temperature of outer heating surfaces) and an ambient airtemperature. In some aspects, a temperature of the heating tubes 120 maybe “set” on the controller 104 and adjustable based on, for example,type of food product 125 placed on the heating tubes 120, “doneness” ofthe food product 125, or otherwise. The controller 104 may vary theelectrical power to the heating elements 151 in order to ensure, forinstance, that food product 125 is properly and safely heated or cooked(e.g., by increasing or maintaining power), as well as to ensure thatfood product 125 does not become overcooked (e.g., by decreasing power).

Turning to FIGS. 1B-1E, end and side views of a portion of the rollergrill 100 are illustrated. As illustrated, the roller grill 100 includespressurized plenums 107 a and 107 b enclosed within the side housings105 a and 105 b in which the direct drive assembly may be disposed. Thedirect drive assembly may drive (e.g., rotate) the heating tubes 120 toheat and/or reheat pre-cooked food product. As illustrated, each heatingtube 120 is installed over a tubular portion of a heating tube gear 140,which in turn, is installed through apertures in the side housing 105. Abushing 135 a may also be installed through the aperture of the sidehousing 105 such that the heating tube 120 is disposed within thebushing 135 a and may move (e.g., rotate) within the bushing 135 a. Insome embodiments, the bushing 135 a may be a paired bushing, such thattwo heating tubes 120 are inserted through a single bushing 135 a.

In the illustrated embodiment, one or more plenum plates 137 (two inthis example) may be installed in the pressurized plenum 107 a. Asillustrated, the plenum plates 137 may be substantially triangular inshape and may extend across a portion of a width of the pressurizedplenum 107 a (as shown in FIG. 1B). The plenum plate 137 may extend fromjust above a midpoint of a set of idler gears 145 (each set in thisexample includes seven idler gears 145) downward to just above amidpoint of a transfer gear 160 that is contactingly engaged with adrive gear 165. In some embodiments, the idler gears 145, as well as oneor more transfer gears 160, may be mounted to the plenum plate 137. Forinstance, the gears 145 and 160 may be mounted through a mechanicalfastener disposed through an axis of the particular gear and through theplenum plate 137. In alternative embodiments, studs may be mounted(e.g., welded) on to the plenum plate 137 over which the gears 145 and160 may be mounted. In any event, the gears 145 and 160 may befree-spinning gears mounted to the plenum plate 137 without penetrationsthrough the side housing 105 (e.g., into a sanitary volume below thepre-cooked food product 125).

FIG. 1B illustrates heating elements 151 (e.g., heaters with spadeterminals 150 a and 150 b) to which wires may be coupled and therebyelectrically coupled to a power source. The heating elements 151 may, insome embodiments, be an electric resistance heater installed through theheating tube 120 (e.g., all or partially) that may generate heat powerto increase a temperature of an outer surface of the heating tube 120.In some embodiments, each heating tube 120 may include an individualheating element 151. Alternatively, heating elements 151 may beinstalled in every other heating tube 120 (e.g., alternating heatingtubes 120) or otherwise.

In the illustrated roller grill 100, the idler gears 145 are mountedbelow and engaged with the heating tube gears 140. Further, theillustrated roller grill 100 includes a drive gear 165 disposed on ashaft 170 of a motor 175 with a fan 178 (shown in FIG. 1D) that may bemounted in a bottom cavity of the roller grill 100 (defined by the sidehousings 105 a and 105 b, the drip plate 180, and the bottom housing110). The drive gear 165 contactingly engages a transfer gear 160 withina series of transfer gears 160 to transfer rotational motion of theshaft 170 to the transfer gears 160. Although three transfer gears 160are illustrated in FIG. 1B per drive gear 165, alternative embodimentsmay include more or fewer transfer gears 160. In some embodiments, oneor more of the transfer gears 160 may be helical spur gears (e.g.,helical gear 800). Further, although two drive sets are shown (e.g., twodrive gears 165 each driven by a motor 175 and in turn drive independentsets of idler gears 145 that are coupled to tube gears 140), otherexample embodiments may include one drive set or more than two drivesets.

In some aspects, the motor 175 (or motors 175 mounted in the rollergrill 100) may be slip gear (or slip clutch) type motors in order to,for example, prevent or help prevent damage to the motor or othercomponents (e.g., one or more gears, belts, chains or otherwise) in theroller grill 100 (or other roller grill described herein). For instance,during cleaning of the drive system of a roller grill (such as one ofroller grills 100, 200, 300, or 400), tension may be placed on the drivesystem by contact with, for instance, the gears, chains, and/or belts.This tension may, in some cases, cause a drive motor to bind, therebydamaging the motor, gears, and/or other components. By using a slipclutch motor, tensions that exceeds an adjustable threshold amount oftension on the motor may cause a rotating shaft of the motor to slip.Thus, a potentially damaging torque transfer to the motor or othercomponents may be avoided.

As illustrated, one of the transfer gears 160 may be engaged with one ormore of a plurality of idler gears 145 disposed across a width of theside housing 105. As illustrated, the idler gears 145 may be spacedevenly across the plenum plate 137. The roller grill 100 also includesheating tube gears 140 that are coupled (e.g., inserted into) torespective heating tubes 120. For example, as illustrated, there may bea 1:1 ratio of heating tube gears 140 and heating tubes 120. In someembodiments, one or more of the idler gears 145 and/or heating tubegears 140 may be helical spur gears (e.g., helical gear 800).

The gears 140, 145, 160, and 165 may, in some embodiments, be spurgears. In some embodiments, the gears 140, 145, 160, and 165 may behelical spur gears. In some embodiments, the gears 140, 145, 160, and165 may be non-metallic, such as, for example, a high-temperatureplastic, In some embodiments, for example, one or more gears 140 may bea high-temperature plastic such as, for example, polystyrene, nylon,TEFLON™, polyethylene, polypropylene, polyvinyl chloride,polytetrafluoroethylene (PTFE), and other plastic material) that has acontinual duty max temperature rating of between about 250° F. (121° C.)and about 500° F. (260° C.). In some embodiments, for example, one ormore gears 145, 160, and/or 165 may be a high-temperature plastic thathas a continual duty max temperature rating of between about 120° F.(49° C.) and about 200° F. (93° C.).

In some embodiments, the gears 140, 145, 160, and 165 (and other rollersdescribed herein, such as gears 225 and 230 and pulleys 325 a, 330 a, assome examples) may be self-lubricating. For example, in some embodimentshaving non-metallic gears 140, 145, 160, and 165, a material that formsthe gears 140, 145, 160, and 165 may be impregnated with or otherwisecontain a lubricant material, such as, for example, silicon, or otherlubricant material. During operation of the roller grill 100, thelubricant material may exude from one or more of the gears 140, 145,160, and 165, thereby providing for decreased failure rates due to lackof lubricant between the gears 140, 145, 160, and 165 and othercomponents (e.g., chains, belts, or other components).

With reference to FIGS. 1B and 1D in particular, a cover plate 143 a maybe slideably mounted over a gasket 153 to at least partially seal thepressurized plenum 107 a from an ambient environment. In some otherexamples, the cover plate 143 a may be coupled to the side housing 105 ain another manner, such as latches, mechanical fasteners, hinged, spotwelding, adhesive, or otherwise. In any event, airflow from thepressurized plenum 107 a to an ambient environment may be substantiallyprevented by the cover plate 143 a. As shown, however, the cover plate143 a may include one or more relief openings 147 that allow someairflow to circulate from the pressurized plenum 107 a to the ambientenvironment. The relief openings 147 may be constant sized aperturesformed in the cover plate 143 a or may be adjustable flow restrictions.

In some aspects, the relief openings 143 may be designed and positionedto help balance air pressures between the pressurized plenum 107 a andat least a portion of the inner volumes of the heating tubes 120 (e.g.,a portion of a total volume of all tubes 120). For example, in order tomaintain a slight positive pressure in the pressurized plenum 107 arelative to the inner volumes of the heating tubes 120, a fan 133 a maybe mounted in the side housing 105 a to circulate air from the ambientenvironment to the pressurized plenum 107 a (e.g., from louveredopenings in the bottom housing 110). The circulated air may increase anair pressure in the pressurized plenum 107 a relative to the ambientenvironment and also relative to an air pressure of the inner volumes ofthe heating tubes 120. In some aspects, the higher pressure plenum 107 a(relative to the inner volumes of the heating tubes 120 which are opento the plenum 107 a) may prevent or help prevent the heat (e.g.,generated by the electric resistance heaters 151 positioned inrespective interior volumes of the tubes 120) from escaping into theplenum 107 a rather than the tube surface and into food product. Therelief openings 143 may be designed, therefore, to prevent or helpprevent overpressurization of the pressurized plenum 107 a by allowing asmall amount of airflow to escape the plenum 107 a into the environment.

In some aspects, relative temperatures and pressures of the pressurizedplenum 107 a and the inner volumes of the heating tubes 120 may bequantified through Gay-Lussac's (Amonton's) law, assuming an idealsituation of constant volume for the pressurized plenum 107 a and theaggregate individual inner volumes of the heating tubes 120.Gay-Lussac's (Amonton's) law states that a pressure exerted on the sidesof a container by an ideal gas of fixed volume is proportional to itstemperature. Thus, as temperature within the fixed volume changes, sodoes pressure according to the equation:

P ₁ /T ₁ =P ₂ /T ₂,

where P₁ and T₁ are pressure and temperature at condition 1, and P₂ andT₂ are pressure and temperature at condition 2.

With reference to the heating tubes 120, and assuming ambienttemperature and pressure (e.g., 75° F. (24° C.) and 14.7 psi (101.3kPa)) at condition 1 (e.g., when the roller grill is not operating), asthe temperature in the tubes 120 reaches a design heating temperature ofabout 240° F. (116° C.) for condition 2 (e.g., when the roller grill hasreached a steady state heating operation), the pressure increases toabout 47.0 psi (324.1 kPa). With reference to the pressurized plenum 107a, therefore, the pressure in the volume of plenum 107 a at condition 2must be slightly greater than the pressure in the volume of the tubes120 at condition 2. Raising the pressure in the plenum 107 a may occurin part due to a rise in temperature in this volume during steady stateoperation of the roller grill 100, but may in more part be due to anairflow circulated to this volume by the fan 133 a. In some aspects, thefan 133 a may circulate about 18 ft³/min (2×10⁻¹² m³/s) to thepressurized plenum 107 a to generate a positive pressure relative to thevolume of the heating tubes 120.

With reference to FIGS. 1C and 1E, which show a non-drive side of theroller grill 100, a cover plate 143 b may be slideably mounted over agasket 153 to at least partially seal the pressurized plenum 107 b froman ambient environment. In some other examples, the cover plate 143 bmay be coupled to the side housing 105 b in another manner, such aslatches, mechanical fasteners, hinged, spot welding, adhesive, orotherwise. In any event, airflow from the pressurized plenum 107 b to anambient environment may be substantially prevented by the cover plate143 b. As shown, however, the cover plate 143 b may include one or morerelief openings 147 that allow some airflow to circulate from thepressurized plenum 107 b to the ambient environment. The relief openings147 may be constant sized apertures formed in the cover plate 143 b ormay be adjustable flow restrictions (e.g., valves, openings withadjustable covers, or otherwise).

In some aspects, the relief openings 143 may be designed and positionedto help balance air pressures between the pressurized plenum 107 b, atleast a portion of the inner volumes of the heating tubes 120 (e.g., aportion of a total volume of all tubes 120), and/or an ambientenvironment that surrounds the roller grill 100. For example, in orderto maintain a slight positive pressure in the pressurized plenum 107 brelative to the inner volumes of the heating tubes 120, a fan 133 b maybe mounted in the side housing 105 a to circulate air from the ambientenvironment to the pressurized plenum 107 b (e.g., from louveredopenings in the bottom housing 110). The circulated air may increase anair pressure in the pressurized plenum 107 b relative to the ambientenvironment and also relative to an air pressure of the inner volumes ofthe heating tubes 120. In some aspects, the higher pressure plenum 107 b(relative to the inner volumes of the heating tubes 120) may prevent orhelp prevent the heat (e.g., generated by the electric resistanceheaters 151 positioned in respective interior volumes of the tubes 120)from escaping into the plenum 107 b rather than the tube surface andinto food product. The relief openings 143 may be designed, therefore,to prevent or help prevent overpressurization of the pressurized plenum107 b by allowing a small amount of airflow to escape the plenum 107 binto the environment. As with the description of the relativetemperatures and pressure of pressurized plenum 107 a described above,the relative temperatures and pressure of pressurized plenum 107 b arelargely similar.

Turning to FIG. 1E, a side view of a non-drive side of the roller grill100 is illustrated. In some embodiments, only one side housing 105 a mayenclose (at least partially) one or more gears and other components ofthe direct drive assembly. In alternative embodiments, both sidehousings 105 a and 105 b may enclose (at least partially) a portion ofone or more (e.g., two) direct drive assemblies as described above. Forexample, there may be two motors 175 per side housing (or one motor 175per side housing) with each motor 175 driving (e.g., rotating) half of atotal number of heating tubes 120 via independent direct driveassemblies. Each independent direct drive assembly may be enclosedwithin separate side housings 105 a and 105 b.

In the illustrated example embodiment, the pressurized plenum 107 benclosed by the side housing 105 b (shown in FIG. 1E) is substantiallyfree of gears and other direct drive assembly components. Asillustrated, the heating tubes 120 may include spade terminals 150 bthat extend from this end of the tube 120 and may extend through theside housing 105 b and be secured to the side housing 105 b by a bushing135 b (as described above). The bushing 135 b may be sandwiched againstan interior surface of the side housing 105 b by a retainer plate 190 b.In the illustrated embodiment, a cover plate 185 b is mounted to theside housing 105 b and adjacent the bushing 135 b. In some embodiments,a bearing 197 may be mounted between the bushing 135 b and the retainerplate 190 b so as to, for example, provide a bearing (e.g., wear)surface between the bushing 135 b and the retainer plate 190 b.

The non-drive side of the roller grill 100 that is shown in FIG. 1E mayinclude a side housing 105 b that takes into account expansion of one ormore of the components due to heat. For example, the tubes 120 and/orheating elements 151 (as well as spade terminals 150 a/150 b) may expandduring a heating or cooking mode of the roller grill 100. This expansionmay be accounted for with, for instance, the bearings 197 do not movebut allow the tubes 120 to turn as well as expand axially. Further, theplenum 102 b may be sized to account for such expansion.

In operation, the motor 175 of the roller grill 100 may rotate the shaft170, which in turn rotates the drive gear 165. The drive gear 165, inturn, transfers rotational movement to the transfer gears 160. One ofthe transfer gears 160 is engaged with one or more of the idler gears145 such that rotational movement is transferred from the transfer gears160 to the engaged idler gear 145. The engaged idler gear 145 is also incontacting engagement with at least one of the heating tube gears 140,and transfers rotational movement to the at least one heating tube gear140. Rotational movement is thus transferred to each of the idler gears145 and heating tube gears 140, thereby rotating the heating tubes 120.

During (and/or after and/or before) operation of the motor(s) 175, thefans 133 a and 133 b may circulate air 163, through openings 167, andinto the respective pressurized plenums 107 a and 107 b to increase anair pressure in the respective plenums. The increased pressure in theplenums 107 a and 107 b may be greater (at least slightly) than apressure in the heating tubes 120. By increasing the pressure in theplenums 107 a and 107 b relative to the pressure in the heating tubes120, heat generated by electric resistance heat 151 in the tubes 120 maynot be transferred into the plenums 107 a and 107 b, or through othercomponents of the grill 100, such as the side housings 105 a and 105 b.Instead, the heat may be transferred through the heating tubes 120 andto heating surfaces of the tubes 120 that are in contact with the foodproduct 125. In some aspects, as most or almost all of the heat istransferred through the tubes 120 rather than, for example, to theplenums 107 a and 107 b, the surface temperature of the tubes 120 may besubstantially consistent across the tubes 120 and across any particulartube 120. For example, temperature variation between any two particularlocations on the tubes 120 may only be between ±2° F. to ±5° F. Further,an air temperature within the pressurized plenums 107 a and 107 b, aswell as of the side housings 105 a and 105 b, may be kept relatively low(e.g., about 90° F. (32° C.)).

Although roller grill 100 is an example of a roller grill that uses afan to pressurize a plenum of a side housing, other pressurizationdevices may be used in place of (or in addition to) a fan thatcirculates a pressurizing airflow to the plenum. Turning briefly toFIGS. 7A-7D, side views of a portion of the roller grill 100 are shown,each of which includes one or more pressurization devices that canpressurize the plenum 102 a as described above. Such pressurizationdevices may also be used, for instance, in the example embodiments ofthe roller grills 200, 300, and 400 described below. Although FIGS.7A-7D only show side views of a drive side of the roller grill 100,similar concepts described and shown in these figures can also beapplied to a non-drive side of the roller grill 100 (e.g., as shown inFIG. 1E).

FIG. 7A shows the roller grill 100 with a compressor 700 coupled to theside housing 105 a and in fluid communication with the plenum 102 a andan ambient environment through louvers 167. The airflow 163 may enter aninlet of the compressor 700 (e.g., centrifugal, scroll, or otherwise),which then raises a pressure of the airflow 163 and circulates thepressurized airflow 163 into the plenum 102 a. In some aspects, apressure limit switch may be part of, or coupled to, the compressor 700,as well as coupled to a pressure sensor 702 (e.g., absolute ordifferential). The limit switch may, in some aspects, control operationof the compressor 700 (e.g., on, off, speed) based on, for instance, thepressure sensor 702. For instance, if the pressure sensor 702 measures apressure in the plenum 102 a (or difference in pressure between theplenum 102 a and another volume of air) that is too large (e.g., anoverpressurization event), then the limit switch may reduce a speed of,or turn off, the compressor 700. Similarly, a pressure limit switch canbe coupled to the fan 133 a (and/or fan 133 b) and function as describedabove.

FIG. 7B shows the roller grill 100 with a compressor 705 coupled to theside housing 105 a through a conduit 710 and through an aperture 715,and in fluid communication with the plenum 102 a and an ambientenvironment through louvers 167. The airflow 163 may enter an inlet ofthe compressor 705, which then raises a pressure of the airflow 163 andcirculates the pressurized airflow 163 into the plenum 102 a. In someaspects, a pressure limit switch 720 may be part of, or coupled to, thecompressor 705, as well as coupled to a pressure sensor 725 (e.g.,absolute or differential). The limit switch 720 may, in some aspects,control operation of the compressor 705 (e.g., on, off, speed) based on,for instance, the pressure sensor 725. For instance, if the pressuresensor 725 measures a pressure in the plenum 102 a (or difference inpressure between the plenum 102 a and another volume of air) that is toolarge (e.g., an overpressurization event), then the limit switch mayreduce a speed of, or turn off, the compressor 705. Although illustratedas within a bottom housing 110 of the roller grill 100, the compressor705 may also be remote from the roller grill 100 or contained in anotherportion of the roller grill 100.

FIG. 7C shows the roller grill 100 with a pressurized air tank 740coupled to the side housing 105 a though a conduit 745 and through anaperture 750 and in fluid communication with the plenum 102 a.Pressurized air tank 740 may controllably release a flow of pressurizedair 163 into the plenum 103 a, which then raises a pressure of theplenum 102 a. In some aspects, a valve 755 may be part of, or coupledto, the tank 740, as well as coupled to a pressure sensor 760 (e.g.,absolute or differential). The valve 755 may, in some aspects, controloperation of the tank 740 (e.g., fully open, fully closed, partiallyopen) based on, for instance, the pressure sensor 760. For instance, ifthe pressure sensor 760 measures a pressure in the plenum 102 a (ordifference in pressure between the plenum 102 a and another volume ofair) that is too large (e.g., an overpressurization event), then thevalve 755 may close or partially close the pressurized air tank 740.Although illustrated as within a bottom housing 110 of the roller grill100, the air tank 740 may also be remote from the roller grill 100 orcontained in another portion of the roller grill 100.

FIG. 7D shows the roller grill 100 with a pump 760 (e.g., a bellows pumpor diaphragm, or otherwise) coupled to the side housing 105 a and influid communication with the plenum 102 a and an ambient environmentthrough louvers 167. The airflow 163 may enter an inlet of the pump 760,which then raises a pressure of the airflow 163 and circulated thepressurized airflow 163 into the plenum 102 a. In some aspects, apressure limit switch (not shown) may be part of, or coupled to, thepump 760, as well as coupled to a pressure sensor (e.g., absolute ordifferential such as the pressure sensor 760). The limit switch may, insome aspects, control operation of the pump 760 (e.g., on, off, speed)based on, for instance, the pressure sensor. For instance, if thepressure sensor measures a pressure in the plenum 102 a (or differencein pressure between the plenum 102 a and another volume of air) that istoo large (e.g., an overpressurization event), then the limit switch mayreduce a speed of, or turn off, the pump 760.

FIGS. 2A-2C illustrate views of an example embodiment of a roller grill200 that includes one or more pressurized plenums and a belt driveassembly with one or more worm gears. FIG. 2A shows that the rollergrill 200 includes a side housing 205 and a bottom housing 210 that isattached to and disposed between lower regions of plates of the sidehousing 205 and a corresponding side housing on an opposite end of theroller grill 200 (not shown). Referring now to FIG. 2B, the weight ofthe roller grill 200 is supported by multiple legs 215 that are mountedunderneath and near corners of the bottom housing 210.

The roller grill 200 includes a pressurized plenum 207 located, asshown, on a drive side of the grill 200. Another pressurized plenum maybe located in a side housing on an opposite side of the roller grill 200(not shown). A fan 209 may be mounted so as to circulate an airflow 211into the pressurized plenum 207. As with the roller grill 100, theairflow into the plenum 207 from the fan 209 may pressurize the plenum207 relative to the heating tubes 220. A side panel 215 may be mountedto the side housing 205, and, as illustrated, against a gasket 217, soas to substantially seal the plenum 207 against undesired airflow intoor out of the plenum 207. For instance, the panel 215 may include one ormore relief openings sized to balance or help balance pressures in theplenum 207 and the heating tubes 220 (e.g., to provide a slight positivepressure in the plenum 207). Generally, the operation of the fan 209 andpressurized plenum 207 may be substantially similar to similarcomponents described above with reference to roller grill 100.

FIGS. 2A-2B illustrate the roller grill 200 further including multipleheating tubes 220 that are disposed parallel to one another, across avolume defined between upper regions of opposite panels of the two sidehousings 205, and above the bottom housing 210. An end of each heatingtube 220 extends through a respective hole within the panel of the sidehousing 205 into a pressurized plenum space 223 provided by the sidehousing 205. In some embodiments, the width of the pressurized plenumspace 223 is approximately 1.625 inches (4.128 cm). Within thepressurized plenum space 223, each heating tube 220 and is engaged witha respective spur gear 225 included within the belt drive assembly. Insome examples, each spur gear 225 is mounted in the end of therespective heating tube 220 and is maintained on the end by a respectivebushing 250 and/or other components. In some examples, the spur gears225 may be helical spur gears. Within the pressurized plenum space 223,the spur gears 225 are further engaged with worm gears 230 disposedadjacent (e.g., beneath) the spur gears 225 and mounted on a shaft 235that extends along at least a portion of the width of the roller grill200.

In some embodiments, the ratio of spur gears 225 to worm gears 230 is1:1. In some embodiments, the ratio of spur gears 225 to worm gears 230is 2:1 or another ratio. In some embodiments, a spur gear 225 may be ahelical spur gear. In some embodiments, a worm gear 230 may be a screwworm gear. In some embodiments, the shaft 235 may be coupled to the sidehousing 205 by one or more bearing blocks 260.

FIG. 2C illustrates that the shaft 235 is further coupled to a timingpulley 240 having multiple teeth disposed on a cylindrical surface thatengage multiple teeth protruding from a surface of a timing belt 245.The timing belt 245 sequentially engages multiple components of the beltdrive assembly that may be fully or partially disposed within the bottomhousing 210 of the roller grill 200. For example, such componentsinclude, as illustrated, a first pulley 255, a timing gear 270 havingmultiple teeth disposed on a circumferential surface and mounted on ashaft of a motor 265, and a second pulley 275 disposed vertically higherthan the first pulley 255. In some examples, one or both of the pulleys255 or 275 can be a timing pulley (i.e., with a grooved circumferentialsurface). In some examples, one or both of the pulleys 255 or 275 mayhave substantially smooth outer cylindrical surfaces.

During operation of the roller grill 200, the motor 265 generates rotarymotion of the heating tubes 220 by using the timing belt 245 to transferrotary motion to the worm gears 230 engaged with the spur gears 225.Power generated by the motor 265 drives rotation of the timing gear 270mounted on the shaft of the motor 265, which, by engagement of the teethdisposed on the surface of the timing gear 270 with the teeth protrudingfrom the surface of the timing belt 245, drives rotation of the timingbelt 245. Thus, in the illustrated embodiment, the timing belt 245extends from the bottom housing 210 through the panel of the sidehousing 205 and into the pressurized plenum space 223 provided by theside housing 205 to engage the timing pulley 240. Alternatively, themotor 265 may be mounted elsewhere in or on the roller grill 200 (e.g.,in the pressurized plenum space 223 or otherwise).

Engagement of the teeth protruding from the surface of the timing belt245 with teeth disposed on the surface of the timing pulley 240 drivesrotation of the timing pulley 240, which in turn rotates the shaft 235.Rotary motion of the shaft 235 drives rotation of the worm gears 230,which consequently drives rotation of the spur gears 225 due to theirengagement with the worm gears 230, and further drives rotation of theheating tubes 220 that are coupled to the spur gears 225.

In some embodiments, one motor 265 may be coupled to two belt driveassemblies located at opposing sides of the roller grill 200. In someembodiments, a first motor 265 may be coupled to a first belt driveassembly located at a first side of the roller grill 200, while a secondmotor 265 may be coupled to a second belt drive assembly located at asecond side of the roller grill 200. In other embodiments, there may betwo (or more) belt drive assemblies, with each assembly driving a subsetof a total number of heating tubes 220 of the roller grill 200. Eachbelt drive assembly may drive the corresponding subset of heating tubes220 from the same end of the roller grill 200 or from opposed ends.

FIGS. 3A-3B illustrate views of another example embodiment of a rollergrill 300 that includes a belt drive assembly and one or morepressurized plenums. The roller grill 300 includes a side housing 305and a bottom housing 370 that is attached to and disposed between lowerregions of panels of the side housing 305 and a corresponding sidehousing on an opposite end of the roller grill 300 (not shown). Theweight of the roller grill 300 is supported by multiple legs 310 thatare mounted underneath and near ends of the bottom housing 370. Theroller grill 300 further includes multiple heating tubes 355 that aredisposed parallel to one another, across a defined volume between upperregions of opposite panels of the two side housings 305, and above thebottom housing 370. The heating tubes 355 are further positionedsufficiently close to one another so as to allow a pre-cooked foodproduct 365 to simultaneously rest atop two adjacent heating tubes 355.One or more annular shaped dividers 360 may be mounted on each heatingtube 355 in order to prevent contact between two pre-cooked foodproducts 365 positioned along common heating tubes 355 or to restrictlateral movement of a pre-cooked food product 365 resting atop theheating tubes 355.

The roller grill 300 includes a pressurized plenum 357 located, asshown, on a drive side of the grill 300. Another pressurized plenum maybe located in a side housing on an opposite side of the roller grill 300(not shown). A fan 303 may be mounted so as to circulate an airflow 307into the pressurized plenum 357. As with the roller grill 100, theairflow 307 into the plenum 357 from the fan 303 may pressurize theplenum 357 relative to the heating tubes 355. A side panel (not shown)may be mounted to the side housing 305 so as to substantially seal theplenum 357 against undesired airflow into or out of the plenum 357. Forinstance, a panel may include one or more relief openings sized tobalance or help balance pressures in the plenum 357 and the heatingtubes 355 (e.g., to provide a slight positive pressure in the plenum357). Generally, the operation of the fan 303 and pressurized plenum 357may be substantially similar to similar components described above withreference to roller grill 100.

In some embodiments, an end of each heating tube 355 extends through arespective hole within the panel of the side housing 305 into apressurized plenum space 357 provided by the side housing 305, where theheating tubes 355 are coupled to one or more belt drive assemblies. Inthis example, the roller grill 300 includes two belt drive assemblies, afirst belt drive assembly 301 a and a second belt drive assembly 301 b.In alternative embodiments, however, the roller grill 300 may includeonly one belt drive assembly or multiple (e.g., two or more) belt driveassemblies. The first belt drive assembly 301 a includes, asillustrated, a timing belt 315 a, multiple timing pulleys 325 a,multiple upper idler pulleys 330 a, two lower idler pulleys 340 a, atensioning pulley 335 a, and a timing gear 345 a. However, inalternative embodiments, the first belt drive assembly 301 a may includemore or fewer of these listed components. The second belt drive assembly301 b includes, as illustrated, a timing belt 315 b, multiple timingpulleys 325 b, multiple upper idler pulleys 330 b, two lower idlerpulleys 340 b, a tensioning pulley 335 b, and a timing gear 345 b.However, in alternative embodiments, the second belt drive assembly 301b may include more or fewer of these listed components.

In the illustrated embodiment, the timing belts 315 a and 315 b includeteeth protruding from a circumferential surface that are adapted toengage teeth disposed on a surface of one or more corresponding timingpulleys 325 a, 325 b. The timing belts 315 a and 315 b are secured onthe one or more corresponding timing pulleys 325 a and 325 b by one ormore bushings 320 a and 320 b. Alternatively, one or both of the timingbelts 315 a and 315 b may be smooth belts, with no teeth or otherprotrusions on a circumferential surface.

In some embodiments, the teeth protruding from a first surface of thetiming belt 315 a, 315 b engage the teeth disposed on the surface of oneor more timing pulleys 325 a, 325 b alternate with a second surface ofthe timing belt 315 a, 315 b engaging one or more upper idler pulleys330 a, 330 b. Following engagement of the timing belt 315 a, 315 b withthe one or more timing pulleys 325 a, 325 b and the one or more upperidler pulleys 330 a, 330 b, the teeth protruding from the surface of thetiming belt 315 a, 315 b engage teeth disposed on a surface of atensioning pulley 335 a, 335 b, which may be mounted on a verticallyadjustable, spring-loaded bracket assembly 343 a, 343 b. The bracketassembly 343 a, 343 b allows the tensioning pulley 335 a, 335 b to beadjusted vertically, thereby further allowing adjustment of tension inthe timing belt 315 a, 315 b. In some embodiments, the roller grill 300may not include the tensioning pulley 335 a, 335 b and the bracketassembly 343 a, 343 b.

In some embodiments, the belt drive assemblies 301 a and 301 b caninclude one or more lower idler pulleys 340 a, 340 b. Followingengagement of the teeth protruding from the surface of the timing belt315 a, 315 b with the teeth disposed on the surface of the tensioningpulley 335 a, 335 b, the teeth protruding from the surface of the timingbelt 315 a, 315 b engage teeth disposed on the surface of the timinggear 345 a, 345 b. The timing gear 345 a, 345 b may be coupled to amotor (not shown) located in the bottom housing 370 of the roller grill300 that drives rotary motion of the timing belt 315 a, 315 b.

In some embodiments, one or more of the upper idler pulleys 330 a, 330 bmay be coupled to a plenum plate 350, which can serve as a heat sinkthat transfers heat away from the timing belt 315 a, 315 b and timingpulleys 325 a, 325 b.

In some embodiments, a louver 375 may be disposed along the bottomsurface of the bottom housing 370, allowing cool air to pass into thebottom housing 370 and cool the motor and any other drive componentsdisposed within the bottom housing.

Referring now to FIG. 3B, in some embodiments, a plenum plate 380 may beattached to each side housing 305, with the plenum 357. Variouscomponents of the drive assembly, such as, for example, the timing gears345 a and 345 b, the idler pulleys 340 a and 340 b, and othercomponents, may be mounted on (e.g., via mechanical fasteners) on theplenum plate 380. The plenum plate 380 may further serve as a heattransfer surface that absorbs heat radiated from the heating tubes 355and the drive assembly components, thereby transferring heat away fromthe drive assembly components. In some embodiments, the plenum plate 380may include one or more ventilation holes 395 allowing fluid (e.g.,airflow) communication between the pressurized plenum 357 and a volumedefined underneath the heating tubes 355 and within the bottom housing210. Such airflow may also be communicated through the louvers 375. Theroller grill 300 may also include multiple bushings 390 that arerespectively mounted over the ends of the multiple heating tubes 355 andthat, for example, prevent the timing pulleys 325 a, 325 b from movinginward on the multiple heating tubes 355. Further, the bushings 390,which may be similar to, for instance, the bushing 900 shown in FIG. 9A,may provide a bearing surface for the heating tubes 355 to rotate withinduring operation of the roller grill 300. In some examples, the plenumplate 380 may have a thermal conductivity that is greater than or equalto 200 Btu/(hr. ft ° F.) (346 W/(m K)) at a temperature of 250° F. (121°C.).

During operation of the roller grill 300, one or more motors (locatedwithin the bottom housing 370, not shown in FIGS. 3A-3B) drive rotationof the heating tubes 355 via the belt drive assemblies 301 a, 301 b. Insome embodiments, a single motor may drive both belt drive assemblies301 a, 301 b. In other embodiments, each belt drive assembly 301 a, 301b (and other belt drive assemblies), may each be driven by a dedicatedmotor.

Power generated by the motor drives rotation of the timing gear 345 a,345 b mounted on a shaft (not shown in FIGS. 3A-3B) of the motor, which,by engagement of the teeth protruding from the surface of the timingbelt 315 a, 315 b with teeth disposed on the surface of the timing gear345 a, 345 b, drives rotary motion of the timing belt 315 a, 315 b.Engagement of teeth protruding from the surface of the timing belt 315a, 315 b with teeth disposed on the surface of the timing pulleys 325 a,325 b further provides rotary motion to the timing pulleys 325 a, 325 b,which consequently rotate the heating tubes 355. Engagement of the teethprotruding from the timing belt 315 a, 315 b with teeth and surface ofthe timing belt 315 a, 315 b disposed on the surface of the idlerpulleys 330 a, 330 b, 340 a, 340 b and the tensioning pulley 335 a, 335b, further rotates the idler pulleys 330 a, 330 b, 340 a, 340 b and thetensioning pulley 335 a, 335 b, respectively.

In some embodiments, the arrangement of the timing pulleys 325 a, 325 band one or more of the idler pulleys 330 a, 330 b, 340 a, 340 b, thetensioning pulley 335 a, 335 b, and the timing gear 345 a, 345 b createsa series of alternating timing belt heating cycles and timing beltcooling cycles, respectively. In some embodiments, the timing beltheating cycles are provided by heat radiated from the timing pulleys 325a, 325 b. When heat is generated within the heating tubes 355 by, forexample, electric resistive heating elements, the heat is transferred tovarious components of the roller grill assembly 300, including thebushings 390 and the timing pulleys 325 a, 325 b. As the timing belt 315a, 315 b engages with the timing pulleys 325 a, 325 b, the timing belt315 a, 315 b absorbs heat from the timing pulleys 325 a, 325 b (i.e.,the timing pulleys 325 a, 325 b transfer heat to the timing belt 315 a,315 b).

In some embodiments, the timing belt 315 a, 315 b may be made from lowheat conducting material. For example, the timing belt 315 a, 315 b maybe insulated from the transfer of heat from, for instance, the heatingtubes 355 through the timing pulleys 325 a, 325 b.

In some embodiments, the timing belt cooling cycles are provided by heatabsorbed by one or more of the idler pulleys 330 a, 330 b, 340 a, 340 b,the tensioning pulley 335 a, 335 b, and the timing gear 345 a, 345 b.For example, as the timing belt 315 a, 315 b engages with the idlerpulleys 330 a, 330 b, 340 a, 340 b, the idler pulleys 330 a, 330 b, 340a, 340 b absorb heat from the timing belt 315 a, 315 b (i.e., the idlerpulleys 330 a, 330 b, 340 a, 340 b transfer heat away from the timingbelt 315 a, 315 b). In some embodiments, the roller grill 300 may notinclude the lower idler pulleys 340 a, 340 b or the tensioning pulley335 a, 335 b. Thus, in some embodiments, the presence of one or more ofthe idler pulleys 330 a, 330 b, 340 a, 340 b and the tensioning pulley335 a, 335 b may determine the length and total cooling effect of thecooling cycle.

In some examples, the thermal conductivity of the timing pulleys 325 a,325 b is less than that of one or more of the idler pulleys 330 a, 330b, 340 a, 340 b, the tensioning pulley 335 a, 335 b, and the timing gear345 a, 345 b. For example, in some embodiments, the thermal conductivityof the timing pulleys 325 a, 325 b may be less than or equal to 17Btu/(hr·ft·° F.) (29 W/(m K)) at a temperature of 250° F. (121° C.),while the thermal conductivity of one or more of the idler pulleys 330a, 330 b, 340 a, 340 b, the tensioning pulley 335 a, 335 b, and thetiming gear 345 a, 345 b may be greater than or equal to 200Btu/(hr·ft·° F.) (346 W/(m K)) at a temperature of 250° F. (121° C.). Insome instances, the cooling cycle can drop the temperature of the timingbelt 315 a, 315 b by up to 50° F. (10° C.). In some examples, thealternating heating cycles and cooling cycles may extend the life of thetiming belt 315 a, 315 b. For example, the cooling cycle may provide thetiming belt 315 a, 315 b with a life of up to six years, whereas a drivechain, in contrast, may need to be changed once per year.

In some embodiments, the timing pulleys 325 a, 325 b may be a low heatconductive material, such as plastic. In some embodiments, the idlerpulleys 330 a, 330 b may be a high heat conductive material, such asaluminum. In some embodiments, the idler pulleys 340 a, 340 b may be alow heat conductive material, such as plastic. In some embodiments, thetiming gear 345 a, 345 b may be a high heat conductive material, such asaluminum.

FIG. 4 illustrates a side view of an example embodiment of a rollergrill 400 that includes a chain drive assembly and one or morepressurized plenums. The roller grill 400 includes two side housings 405(one shown in FIG. 4), and the weight of the roller grill 400 issupported by multiple legs 410 that are mounted underneath and nearcorners of a bottom housing. The roller grill 400 also includes multipleheating tubes and multiple sprockets 420 that are respectively coupledto ends of the multiple heating tubes. In some embodiments, a chain 415provides rotary motion to the heating tubes by engaging the sprockets420. The chain 415 is driven by one or more motors within a bottomhousing of the roller grill 400 (not shown in FIG. 4) as the chain 415engages a drive gear 430 coupled to the motor. In this example, theroller grill 400 includes one chain drive assembly; however, inalternative embodiments, the roller grill 400 may include more than onechain drive assembly.

In some embodiments, one motor may be coupled to two chain driveassemblies located at opposing sides of the roller grill 400. In someembodiments, a first motor may be coupled to a first chain driveassembly located at a first side of the roller grill 400, while a secondmotor may be coupled to a second chain drive assembly located at asecond side of the roller grill 400.

The roller grill 400 includes a pressurized plenum 407 located, asshown, on a drive side of the grill 400. Another pressurized plenum maybe located in a side housing on an opposite side of the roller grill 400(not shown). A fan 403 may be mounted so as to circulate an airflow intothe pressurized plenum 407. As with the roller grill 100, the airflowinto the plenum 407 from the fan 403 may pressurize the plenum 407relative to the heating tubes of the roller grill 400. A side panel (notshown) may be mounted to a side housing so as to substantially seal theplenum 407 against undesired airflow into or out of the plenum 407. Forinstance, a panel may include one or more relief openings sized tobalance or help balance pressures in the plenum 407 and the heatingtubes of the roller grill 400 (e.g., to provide a slight positivepressure in the plenum 407). Generally, the operation of the fan 403 andpressurized plenum 407 may be substantially similar to similarcomponents described above with reference to roller grill 100.

FIGS. 5A-5B illustrate views of example embodiments of a roller grilltube assembly 500, 550 that may be used with a roller grill, such as oneor more of roller grills 100, 200, 300 and/or 400. Referring now to FIG.5A, in some embodiments, a roller grill tube assembly 500 includes aheating tube 505, a sprocket 510 coupled to an end of the heating tube505, and a bushing 515. In some embodiments, the sprocket 510 isinstalled over the heating tube 505 (e.g., press fit over the tube 505).In some embodiments, the bushing 515 may be a bearing inserted into thesprocket 510 that acts as a thrust bearing that prevents (all orpartially) metal-to-metal contact between the sprocket 510 and othermetal components of a roller grill.

In some examples, the sprocket 510 may allow the roller grill tubeassembly 500 to operate with a roller grill utilizing a chain driveassembly, such as the roller grill 400. During operation of a rollergrill, the bushing 515 provides a surface to transfer heat away from theheating tube 505 and the sprocket 510, thereby reducing the wear of thesprocket 510 and a chain (e.g., the chain 415) engaged with the sprocket510. In some embodiments, the bushing 515 can include a notch 520 thatengages with a ridge of the heating tube 505 or a ridge of the sprocket510 to prevent or reduce slippage of the bushing 515. In some examples,the bushing 515 is a TEFLON™ bushing.

Referring now to FIG. 5B, in some embodiments, a roller grill assembly550 may include a heating tube 555, a pulley flange 560 coupled to anend of the heating tube 555, a timing pulley 565 coupled to the end ofthe heating tube 555, and a bushing 570. The bushing 570 may, in someembodiments, extend past the timing pulley 565 to contact a retainerplate (not shown), such as, for instance, the cover plate 280. In someembodiments, the bushing 570 may be TEFLON™ or another bearing material.In some embodiments, the timing pulley 565 may allow the roller grilltube assembly 550 to operate with a roller grill utilizing a belt driveassembly, such as the roller grill 300. In some examples, the pulleyflange 560 may prevent the timing pulley 565 from sliding inward on theheating tube 555. In some examples, the pulley flange 560 is made ofplastic (e.g., TEFLON™) or steel (e.g., stainless or carbon).

FIGS. 6A-6D illustrate an example helical gear 600 that may be used in aroller grill, such as, for example, the roller grill 200 illustrated inFIGS. 2A-2D. In some embodiments of the roller grill 200, for instance,the helical gear 600 may be coupled to a heating tube 220 (or otherheating tube) and used to drive (e.g., rotate) the heating tube 220. Forexample, the helical gear 600 may be driven by the spur gear 225 andmounted on the shaft 235.

As illustrated, the helical gear 600 includes an outer diameter surface610 coupled to (e.g., attached to or integral with) a gear head 605having multiple teeth 615 disposed around an outer surface of the gearhead 605. A bore 620 extends through the gear head 605 and outerdiameter surface 610 and shares a centerline with the gear head 605 andthe outer diameter surface 610. As illustrated, the teeth 615 may beangled to form a helical gear (e.g., at about a 5° angle offset). Insome embodiments, there may be 21 teeth 615, with each tooth 615 havinga pitch diameter of about 1.2 inches (3.1 cm), an outside diameter ofabout 1.3 inches (3.3 cm), a root diameter of about 1.1 inches (2.7 cm),and a tooth thickness at the pitch diameter of about 0.1 inches.Further, in some embodiments, the diameter of the bore 620 is about 0.75inches (1.9 cm).

As illustrated in FIG. 6D, an end of the helical gear 600 that may becoupled to a heating tube includes a beveled surface 625 around acircumference of the outer diameter surface 610. In some embodiments,the beveled surface 625 may be set-off at an angle of about 30° from aninterior surface of the outer diameter surface 610. Alternatively, otherangular offsets are possible. In some embodiments, the beveled surface625 may allow a heating element to be more easily inserted through thehelical gear 600 from the heating tube 220.

As further illustrated in FIG. 6D, the gear head 605 also includes abeveled surface 630 around a circumference of the gear head 605. In someembodiments, the beveled surface 630 may be set-off at an angle of about45° from an interior surface of the gear head 605. Alternatively, otherangular offsets are possible. In some embodiments, a retainer or coverplate (such as the retainer plate 930) may include a concave portion 935that protrudes into the gear head 605 adjacent the beveled surface 630.Thus, there may be more space allowed for wiring coupled to a heatingelement passing through the heating tube 220.

In some embodiments, the helical gear 600 may be coupled to the heatingtube 220 (or another heating tube) as follows. First the outer diametersurface 610 may be inserted (e.g., all or partially) into the heatingtube 220 until an end of the heating tube 220 is at or adjacent the gearhead 605. Next, the heating tube 220 may be punched into the outerdiameter surface 610 (e.g., by compressing the heating tube 220 into theouter diameter surface 610 and/or inserting a davit (not shown) throughthe heating tube 220 and outer diameter surface 610). Next, the assemblyincluding the helical gear 600 and heating tube 220 may be rotated, forexample, about 180°. The heating tube 220 may be punched again into theouter diameter surface 610 (e.g., by installing the heating tube 220over the outer diameter surface 610) at a location about 180° about fromthe first punch location. In such a manner, the helical gear 600 may becoupled to the heating tube 220.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made. For example, variouscombinations of the components described herein may be provided forembodiments of similar apparatus. For instance, although belts andchains are shown in the illustrated embodiments, other types of loopedsurfaces (e.g., continuous looped surfaces) may be used in place ofbelts or chains. Accordingly, other embodiments are within the scope ofthe present disclosure.

I claim:
 1. A method, comprising: providing a roller grill, the rollergrill comprising: a housing structure adapted to support the rollergrill; a plurality of tubular heating surfaces mounted between a firstend of the housing structure and a second end of the housing structure,and to a drive assembly; a first side housing coupled to the first endof the housing structure; and a second side housing coupled to thesecond end of the housing structure; rotatably driving the plurality oftubular heating surfaces with the drive assembly; pressurizing a plenumenclosed within one of the first or second side housings; andmaintaining, based on the pressurization, a plenum air pressure greaterthan a tubular air pressure of an inner volume of the plurality oftubular heating surfaces.
 2. The method of claim 1, wherein pressurizinga plenum enclosed within one of the first or second side housingscomprises: circulating an airflow into the plenum with a fan coupled tothe housing structure and in airflow communication with the plenum andan ambient environment that surrounds the roller grill.
 3. The method ofclaim 2, further comprising: mounting a cover plate mountable to the oneof the first or second side housings that encloses the plenum; and atleast partially sealing against an airflow between the plenum and theambient environment independent of the airflow into the plenum.
 4. Themethod of claim 3, further comprising: providing at least one reliefopening in the cover plate; and flowing a portion of the airflow fromthe plenum through the relief opening.
 5. The method of claim 4, furthercomprising adjusting an opening area of the relief opening based on atleast one of the plenum air pressure or the tubular air pressure.
 6. Themethod of claim 2, further comprising: circulating a second airflow intoa second plenum enclosed within the other of the first or second sidehousings; and maintaining, based on the second airflow circulation, asecond plenum air pressure greater than the tubular air pressure of theinner volume of the plurality of tubular heating surfaces.
 7. The methodof claim 6, wherein circulating a second airflow into a second plenumenclosed within the other of the first or second side housingscomprises: circulating the second airflow into the second plenum with asecond fan coupled to the housing structure and in airflow communicationwith the second plenum and the ambient environment that surrounds theroller grill.
 8. The method of claim 1, wherein a surface temperaturemeasured along a length of a first tubular heating surface of theplurality of tubular heating surfaces is within a range of between ±2°F. and ±5° F.
 9. The method of claim 1, wherein rotatably driving theplurality of tubular heating surfaces with the drive assembly comprises:driving a drive gear with a motor; driving at least one transfer gearwith the drive gear; driving at least one idler gear with the transfergear; and driving at least one tube gear with the idler gear.
 10. Themethod of claim 9, wherein at least one of the drive gear, the transfergear, the idler gear, or the tube gear comprises a non-metallic gear,and the drive assembly comprises a beltless and chainless driveassembly.
 11. The method of claim 1, wherein rotatably driving theplurality of tubular heating surfaces with the drive assembly comprises:driving a drive gear with a motor; moving a belt or chain with the drivegear; driving at least one tube gear with the moving belt or chain. 12.The method of claim 1, wherein rotatably driving the plurality oftubular heating surfaces with the drive assembly comprises driving theplurality of tubular heating surfaces with a slip clutch motor.